The leak was detected in a "choke line" leading from the stack of valves that makes up the cap installed July 12 on the Macondo well, BP said in a statement yesterday. BP said the leak had been “isolated” and was being repaired, BusinessWeek reports.

But by Thursday morning, the live video of the rig showed oil was still billowing from the top of the tap. A BP spokesman said the company had found a leak on the line attached to one of the valves, and that they were repairing it before moving forward.

It was not clear how the discovery of the leak would affect the timing of the planned tests on the well.

Thad W. Allen, the retired Coast Guard admiral who is leading the response, said that the test results would provide crucial information about the well’s condition, and "would determine our confidence to shut the well in and understand we’re not harming the well bore," New York Times informs.